An optical loupe is a small magnification device with a set of lenses through which a user can view an enlarged appearance of a scene under examination, thereby allowing the user to clearly distinguish small details in the scene. Such magnification devices are widely used in a variety of applications and technical fields, ranging from photography, printing and jewelry, to medicine and dentistry. For example, when performing a medical procedure, such as a surgical operation (e.g., heart surgery, brain surgery, plastic surgery), the medical practitioner may use at least one loupe in order to magnify the treatment area. In particular, two separate loupes may be applied to each eye. The loupe(s) may be held by the user and positioned near his eye only when required, or alternatively may be permanently affixed in his field of view, such as being mounted onto spectacles or wearable head gear. However, such a configuration may distract the user and obstruct his peripheral vision. Handling the loupes can be cumbersome and provide surplus weight when worn by or affixed to the user. The loupes are also prone to falling off, breaking, and degradation over time. In addition, a standard loupe typically provides a magnification factor of about 4-5×, which may be insufficient when needing to examine extremely minuscule objects. Moreover, since each loupe is associated with a fixed magnification factor, it is not possible for a user to selectively adjust the desired magnification according to the particular usage, without replacing it with a different loupe entirely. Loupes also have a fixed focus distance, obligating the user to maintain his head at a predefined distance from the object. As the magnification of the loupe increases, the stability of the viewable magnified image is degraded.
The development of wearable imaging devices and wearable display devices has progressed substantially in recent years, leading to a wide variety of systems and products that incorporate such devices. For example, a head-mounted camera can be used to capture images for different applications, such as capturing real-time imagery of an environment in accordance with the changing positions and movements of the wearer. A head-mounted display (HMD) includes display optics disposed in front of one eye (monocular) or both eyes (binocular) of the user, affixed by means of wearable head or eye gear (e.g., helmet, eyeglasses, goggles, contact lenses). The display optics can be positioned directly in the eye line-of-sight (LOS) to provide a direct view, or deviated from the LOS to provide a glancing or peripheral view. A see-through HMD can direct artificial imagery to the wearer while allowing a transparent view of the surrounding environment. For example, supplementary visual content may be projected onto the HMD superimposed onto the background view for enhancing perception of the real-world environment, which is known as augmented reality. The supplementary content is typically presented in real-time and in the context of elements in the current environment.
A wearable camera or wearable display may be subject to vibrations and movements which can cause eye fatigue, nausea, and disorientation, precluding the user from being able to distinguish small details in the image and thus decreasing the effective resolution. These vibrations, caused by small and large head movements, can result in linear and rotational displacement of the image, which may significantly alter which content remains viewable within the image. Compensating for these vibrations in order to obtain a stabilized image may be achieved by mechanical techniques to stabilize the camera, and/or by image processing techniques to stabilize the acquired images. In some applications, users may want to view a video captured by the camera in real-time. In these cases, the wearable display can project the image directly from the wearable camera. When a user wants to observe and focus his sight on a particular object, he may direct the head-mounted camera to a certain LOS and try to maintain conformity with the current field of view associated with his head position and head direction. However, the head movements and camera vibrations diminish the user's ability to maintain focus on small details of the object. In particular, when the images projected onto the display are magnified, the effects of the head and camera movements are amplified in the resultant image vibrations. Alternatively, the user may want to maintain focus on the object of interest while keeping the object located in a convenient zone on the display, regardless of his current head position and direction.
U.S. Pat. No. 6,307,526 to Mann, entitled “Wearable camera system with viewfinder means”, is directed to an apparatus that includes an electronic camera borne by headgear, and an electronic display borne by the headgear. The display is responsive to an electronic output from the camera, providing a viewfinder for the camera. A mirror is arranged to divert light that would otherwise enter an eye of a wearer to the camera, and to divert light emitted from the display to the eye of the wearer, such that diverted light from the display is collinear with light that would otherwise enter the eye. A beam splitter is positioned between the mirror and the eye. A polarizer in front of the camera is oriented to block polarized light emitted by the display.
U.S. Pat. No. 6,847,336 to Lemelson et al, entitled “Selectively controllable heads-up display system”, is directed to a heads-up display system for use by a medical technician. The system includes a command computer processor for receiving inputs that represent data and for controlling the display of desired data. The computer communicates with and controls the heads-up display system, which is configured to display the desired data in a manner that is aligned in the user's field of view. The heads-up display includes a user interface incorporating “hands-free” menu selection to allow the user to control the display of various types of data. The hands-free menu selection may be carried out using an eye-tracking cursor and a speech recognition computer to point to and select specific menus and operations.
U.S. Pat. No. 8,138,991 to Rorberg et al, entitled “Real-time image scanning and processing”, is directed to an apparatus for displaying an image with respect to a line-of-sight (LOS) with substantially no latency as perceived by a user. An image source provides a spatially unregistered image. A display processor spatially registers the image with the LOS. A displaying unit displays at least one spatially registered pixel on a displaying surface. An image processor selects at least one projection pixel to be displayed, and a pixel locator of the display processor determines, in each spatially unregistered image, the location of the spatially registered pixel corresponding to the selected projection pixel.
U.S. Pat. No. 8,611,015 to Wheeler et al, entitled “User interface”, is directed to a head-mounted display (HMD) with an eye-tracking system, an HMD-tracking system, and a display configured to display virtual images to a wearer of the HMD. The virtual images may be dynamically adjusted based on the HMD-tracking data. The eye-tracking data is incorporated to compensate for drift in the displayed virtual images introduced from position and orientation sensor errors of the HMD-tracking system. In particular, the eye-tracking data may be used to determine a gaze axis and a target object in the displayed virtual images. The HMD may then move the target object towards a central axis. The HMD may record data based on the gaze axis, central axis, and target object to determine a user interface preference. The user interface preference may be used to adjust similar interactions in the HMD.
U.S. Pat. No. 8,669,919 to Ono, entitled “Head mounted display device”, is directed to a head-mounted display device that provides a user with information while taking an image in a direction of his field of view. An image display mounted on the head of a user permits the views to visually recognize an image. An imager takes an image in a direction of a field of view of the user and generates a taken moving image. Unitary display image data to be displayed on the image display is acquired. A unitary moving image correlated with the unitary display image is generated from the moving image. When any other unitary moving images correlated with the same unitary display image corresponding to one of the unitary moving images are generated, it is determined whether to replace one of the unitary moving images with any other of the unitary moving images. When it is determined to replace a unitary moving image, it is replaced, while the unitary moving images that are not replaced are combined to generate a coherent continual moving image.